The comments in this background section are not an admission that anything discussed in this section is citable as prior art or part of the common general knowledge of persons skilled in the art in any country.
Some systems for cell cultivation have been developed which provide in some way for the supply of nutrient media to, and the removal of metabolic waste products from, a cell culture. In some systems, cells have been supported on hollow plastic fibers inside of bioreactors. Literature discussing cell cultivation includes the following (1) Sauer, I. M. et al.: The Slide Reactor—a simple hollow fiber based bioreactor suitable for light microscopy; Artificial Organs 29 (3): 264-267, 2005; (2) Sauer, I. M. et al.: Development of a hybrid liver support system. Ann NY Acad Sci 944: 308-19, (2001); Millis, J. M: et al.: Initial experience with the modified extracorporeal liver-assist device for patients with fulminant hepatic failure: system modifications and clinical impact. Transplantation 74: 1735-46; (2002); and, (4) Glöckner, H. et al.: New miniaturized hollow fiber bioreactor for in vivo like cell culture, cell expansion and production of cell-derived products. Biotechnol Prog 17: 828-31 (2001).
PCT Publication No. WO 2004/024303 A2, and related U.S. Publication No. 2006/0014274 A1, disclose a fiber cassette having a housing that is delimited by two congruent base surfaces and at least one circumferential surface and has an interior having at least one cavity. At least one layer of fibers is arranged in the interior of the housing essentially parallel to at least one center plane of the housing, wherein ends of the fibers are anchored fixedly in the interior of the housing. A first one of the at least one cavity defines an outer compartment that surrounds the fibers externally. The at least one center plane does not intersect the base surfaces within the outer compartment. The fibers are arranged U-shaped or essentially parallel to one another and end within the interior of the housing. The housing has at least one opening for supplying and/or removing fluids. PCT Publication No. WO 2004/024303 A2 and U.S. Publication No. 2006/0014274 are incorporated herein in their entirety by this reference to them.